Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
tu sach » thu sach, su sach, te sach
hai cua » thai cua, hoi cua, lai cua
dua ban » dia ban, cua ban, qua ban
cam dua » ca dua, cay dua, chay dua
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
va cam » va cham, va cac, va cao
ma hoi » xa hoi, ma hoa, me hoi

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang ((ma hoi) OR (mai hoi)). hieu va cam dua ban thanh ((hai cua) or (dai cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((ma hoi) OR (mai hoi)). hieu va cam dua ban thanh ((hai cua) OR (dai cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((ma hoi) OR (mai hoi)). hieu va cam dua ban thanh ((hai cua) or (dai cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((ma hoi) OR (mai hoi)). hieu va cam dua ban thanh ((hai cua) or (dai cua)) tre*.